1. Field of the Invention
The present invention relates to a process for the preparation of surface active agents for use in disperse dyes and, more particularly, to a process for the preparation of such surface active agents which exhibit excellent dispersing power in high temperature dyeing with water-insoluble disperse dyes for synthetic fibers, as well as little or no cellulose staining in dyeing a synthetic fiber/cellulosic fiber blended yarn fabric by the thermosol process.
The term "disperse dyes" is used herein to indicate water-insoluble disperse dyes for use in dyeing synthetic fibers and disperse dyes of the azoic type.
2. Description of the Prior Art
In the field of dyeing of polyester fibers there is most commonly used, in general, a high temperature dyeing process wherein the fibers are dyed with a water-insoluble disperse dye under pressure at elevated temperatures.
Recently, with the increasing production of polyester textured yarn, instances wherein a textured yarn is the substrate to be dyed have been increasing, and this has given rise to many dyeing problems, all resulting from the properties of the textured yarn. Of these problems, the problem of level dyeing if of particular importance. In general, when a textured yarn is subjected to high temperature dyeing with a water-insoluble disperse dye, an unsatisfactory dyeing level is often obtained. In order to improve the dyeing level performance, surface active agents, called levelling agents, are often added during dyeing. These levelling agents consist usually of nonionic or anionic surface active agents and are used in such great amounts that although, through the use of these agents, the dyeing level effect on polyester textured yarns or fabrics made therefrom is satisfactorily performed, the dispersed condition of the finely granulated dye tends to be destroyed in the course of the dyeing procedure, resulting in aggregation of the finely granulated dye which in turn causes many problems. In addition, the levelling agents, having a retarding action, often reduce the dyeing depth of the substrate.
As a surface active agent having dispersing power at high temperatures there has previously been used the surface active agent described in PB Report 101462 which is obtained by reacting, in water as solvent and under pressure, cresol, formalin, sodium sulfite, the sodium salt of Schaffer's acid (2-hydroxynaphthalene-6-sulfonic acid) and sodium hydroxide. This surface active agent, when used in finely granulating a dye, exhibits good dispersing power under alkaline conditions but remarkably reduced dispersing power under acidic or neutral conditions. Furthermore, when used in high temperature dyeing in the presence of a levelling agent, it shows inadequate dispersing power at high temperatures. In addition, its production process is a reaction under pressure, so that the operation is extremely intricate.